Intracellular recording of light-evoked electrical potentials will be used in quantitative studies designed to further delineate retinal mechanisms of vision. Primary emphasis centers upon the influence of lateral pathways of the distal retina and the role which they play in visual contrast and discrimination. By exploiting special advantages offered by the retina of the walleye (Stizostedion vitreeum vitreeum), a series of interrelated experiments will be performed on L-type horizontal cells, C-type horizontal cells, and cones. These experiments will characterize the joint effects of spectral and spatial stimulus variables upon these cellular responses, and are specifically designed to yield evidence necessary to further clarify the role of receptors and L-type horizontal cells in establishing mechanisms for spatial and spectral antagonism in the retina.